The liquid crystal diffraction grating includes: paired substrates each including an electrode; a liquid crystal layer being held between the substrates; a sealant; and an alignment-controlling layer being disposed in a region surrounded by the sealant in a plan view and being in contact with the liquid crystal layer between the liquid crystal layer and each of the substrates, the alignment-controlling layer being configured to align liquid crystal molecules in a direction parallel to the substrates and containing a polymer of at least one monomer, the orientation of the liquid crystal molecules periodically rotating in at least one direction in a plan view of the liquid crystal layer in a state where the liquid crystal molecules are aligned in the direction parallel to the substrates.